I've seen something that sounds related. In grep, in the en_US.UTF-8 locale, sometimes I can match [A-Z]+ and it will match accented uppercase strings such as "

I've seen something that sounds related. In grep, in the en_US.UTF-8 locale, sometimes I can match [A-Z]+ and it will match accented uppercase strings such as "SCHÖN". It will not match lowercase letters. This is often desirable, except for the part that I don't know what the heck ranges mean anymore. "Ö" is certainly not between "A" and "Z" in codepoint order. It is in collation order, but if it were collation order, it would match lowercase letters. How does this work?